Uplink multi-TTI scheduling in TDD system

ABSTRACT

Systems and methods are disclosed for transmission and reception of an uplink grant during a gap created in radio resources assigned by a previous multiple Transmit Time Interval (multi-TTI) uplink grant in a system operating according to a Time Division Duplexing (TDD) scheme. In one embodiment, a method of operation of a radio network node in a cellular communications network is provided. The method includes transmitting a first uplink grant that assigns radio resources for a multi-TTI uplink transmission, and transmitting a second uplink grant during a gap in the radio resources assigned by the first uplink grant. In one embodiment, by utilizing the gap to transmit the second uplink grant, uplink radio resources assigned for uplink transmission can be maximized, which is particularly beneficial in high uplink traffic conditions.

RELATED APPLICATIONS

This application is a continuation of patent application Ser. No.14/212,927, filed Mar. 14, 2014, now U.S. Pat. No. 9,942,881, thedisclosure of which is hereby incorporated herein by reference in itsentirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a cellular communications network and,in particular, multiple Transmit Time Interval (multi-TTI) uplinkscheduling in a Time Division Duplexing (TDD) system.

BACKGROUND

Some important features in future cellular communications networks arehigher bitrates and shorter delays applied to small cell scenarios.Higher bitrates can, for example, be achieved by using higher carrierfrequencies where wideband spectrum resources are available. Inaddition, Time Division Duplexing (TDD), and in particular dynamic TDD,has attained an increased interest because downlink or uplink bitratescan be instantaneously increased by adaptively changing the relationbetween the number of intervals used for the downlink and the uplink.

In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)Release 11 (Rel-11), the downlink is based on Orthogonal FrequencyDivision Multiplexing (OFDM) while the uplink is based on DiscreteFourier Transform (DFT) spread OFDM, i.e. Single Carrier FrequencyDivision Multiple Access (SC-FDMA), see, for example, 3GPP TechnicalSpecification (TS) 36.211, Evolved Universal Terrestrial Radio Access(E-UTRA); Physical Channels and Modulation, V11.3.0. Here, theTransmission Time Interval (TTI) equals a subframe of 1 millisecond(ms), which consists of 14 OFDM symbols in the downlink and 14 SC-FDMAsymbols in the uplink for the user data in the Physical Downlink SharedChannel (PDSCH) and the Physical Uplink Shared Channel (PUSCH) withnormal length of the cyclic prefix. In future cellular communicationsnetworks, the length of a subframe might be significantly reduced inorder to reduce user data delays. Also, the uplink and downlink ratiosin future TDD systems may be significantly better optimized to varioustypes of traffic supporting much larger uplink and downlink asymmetriesthan today. The switching between downlink and uplink is typically doneon a subframe basis. Furthermore, in future cellular communicationssystems, both the downlink and the uplink might be based on the sameradio access technology, such as, for example, OFDM or SC-FDMA.

When using TDD, the same frequency is used for both a downlink from abase station to a wireless device and an uplink from the wireless deviceto the base station. Both the wireless device and the base station mustswitch between transmitting and receiving, assuming that full duplexoperation is not possible. Further, in 3GPP LTE Rel-11, a fixedallocation of uplink and downlink subframes is used, as specified in3GPP TS 36.211 V11.3.0. A few predefined allocations are specified in3GPP LTE Rel-11, as illustrated in FIG. 1. The number of uplinksubframes for user data transmission in each 10 ms radio frame isbetween 1 and 6, which means a maximum of 60% of the total subframes ineach radio frame can be used for uplink traffic. Here, a specialsubframe is inserted between downlink and uplink subframes, asillustrated in FIG. 2. The special subframe contains OFDM and SC-FDMAsymbols for the downlink and the uplink, respectively, with a GuardPeriod (GP) in between. The guard period provides time for transmit andreceive circuitry of the base station to switch from downlinktransmission to uplink reception and time for transmit and receivecircuitry of the wireless device to switch from downlink reception touplink transmission.

The radio network node sends control signaling to the wireless devicethat includes a downlink assignment that indicates when and how thewireless device is scheduled to receive in the downlink and an uplinkgrant that indicates when and how the wireless device is to transmit inthe uplink. In LTE, this control signaling is carried by either thePhysical Downlink Control Channel (PDCCH) or the Enhanced PDCCH(EPDCCH). The downlink assignment is transmitted in the same subframe ofthe downlink in which the corresponding user data is transmitted.Conversely, the uplink grant is transmitted in the downlink a fewsubframes before the wireless device is scheduled to transmit in theuplink. More specifically, as illustrated in FIG. 3, if an uplink grantis transmitted in downlink subframe n, the wireless device can startuplink transmission in subframe n+g, where g is an uplink schedulingdelay. For LTE TDD, the minimum uplink scheduling delay (g) is foursubframes, which corresponds to 4 ms. However, the actual uplinkscheduling delay depends on the uplink/downlink subframe allocation. So,in some cases, the uplink scheduling delay (g) can be larger than 4 ms.For instance, in the example of FIG. 3, an uplink grant is transmittedin the downlink in subframe 1 in order to grant radio resources for anuplink transmission in subframe 7. In this case, the uplink schedulingdelay (g) is 6 subframes, which is equivalent to 6 ms. Likewise, in thisexample, an uplink grant is transmitted in the downlink in subframe 9 inorder to grant radio resources for an uplink transmission in subframe13. In this case, the uplink scheduling delay (g) is 4 subframes, whichis equivalent to 4 ms. For more information regarding uplink scheduling,the interested reader is directed to 3GPP TS 36.213, Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical layer procedures (Release11), V11.3.0.

Multiple Transmit Time Interval (multi-TTI) uplink grants are supportedin LTE TDD uplink/downlink configuration 0. As illustrated in FIG. 4, amulti-TTI uplink grant schedules uplink transmissions in multiple uplinksubframes. Currently, a maximum of two uplink subframes are scheduledwith one multi-TTI uplink grant, as specified in 3GPP TS 36.213 V11.3.0.In the particular example of FIG. 4, a multi-TTI uplink grant istransmitted in the downlink in subframe 1 in order to grant uplinkresources in subframes 7 and 8. Similarly, a multi-TTI uplink grant istransmitted in the downlink in subframe 5 in order to grant uplinkresources in subframes 9 and 12.

In a dynamic TDD system, the relation between the number of downlinksubframes and uplink subframes is not fixed, but can be flexiblyconfigured depending of the current need. For example, thedownlink/uplink configuration can be dynamically signaled, oralternatively, a wireless device can treat a subframe as a downlinksubframe unless explicitly instructed to transmit in the uplink, asdescribed in commonly held and assigned U.S. Pat. No. 8,559,343 entitledFLEXIBLE SUBFRAMES, issued Oct. 15, 2013.

In future cellular communications networks with high density deploymentand higher carrier frequency, the coverage area of a radio network nodecan be small. Hence, the number of wireless devices connected to eachradio network node in the network can be low and the traffic in thenetwork can change dramatically. In the extreme case, the traffic for agiven cell served by a radio network node can be only download trafficor only upload traffic at a given point in time. This presents newproblems that are not addressed in the present 3GPP LTE standards.

SUMMARY

Systems and methods are disclosed for transmission and reception of anuplink grant during a gap created in radio resources assigned by aprevious multiple Transmit Time Interval (multi-TTI) uplink grant in asystem operating according to a Time Division Duplexing (TDD) scheme. Inone embodiment, a method of operation of a radio network node operatingaccording to a TDD scheme in a cellular communications network isprovided. The method of operation of the radio network node includestransmitting a first uplink grant that assigns first radio resources fora first multi-TTI uplink transmission, and transmitting a second uplinkgrant during a gap in the first radio resources assigned by the firstuplink grant for the first multi-TTI uplink transmission. In oneembodiment, the second uplink grant assigns second radio resources for asecond multi-TTI uplink transmission. In one embodiment, by utilizingthe gap to transmit the second uplink grant, uplink radio resourcesassigned for uplink transmission can be maximized, which is particularlybeneficial in high uplink traffic conditions.

In one embodiment, the first radio resources assigned by the firstuplink grant comprise a first set of consecutive subframes, and the gapin the first radio resources comprises a gap subframe within the firstset of consecutive subframes.

In one embodiment, the gap is a time domain gap (e.g., a subframe), anda position of the gap is a position relative to an end of the firstradio resources assigned by the first uplink grant for the firstmulti-TTI uplink transmission. Further, in one embodiment, an amount oftime between the gap and the end of the first radio resources is greaterthan or equal to an uplink scheduling delay.

In one embodiment, the gap is a time domain gap, and a position of thegap is defined by a cellular communications network standard. In anotherembodiment, the method of operation of the radio network node furtherincludes signaling a position of the gap to a wireless device. In oneparticular embodiment, signaling the position of the gap to the wirelessdevice includes signaling the position of the gap to the wireless devicevia Radio Resource Control (RRC) signaling.

In one embodiment, a position of the gap is semi-statically configured.Further, in one embodiment, a position of the gap is semi-staticallyconfigured individually for a wireless device. In another embodiment, aposition of the gap is semi-statically configured for a plurality ofwireless devices.

In another embodiment, the method of operation of the radio network nodefurther includes dynamically configuring the gap. In one embodiment,dynamically configuring the gap comprises providing a position of thegap in the first uplink grant. In another embodiment, dynamicallyconfiguring the gap includes providing an indication of the gap in thefirst uplink grant.

In one embodiment, the method of operation of the radio network nodefurther includes, prior to transmitting the second uplink grant duringthe gap, determining whether the gap is to be used. The method furtherincludes transmitting the second uplink grant during the gap in responseto determining that the gap is to be used. In one embodiment, the methodof operation of the radio network node further includes determining thatthe gap is to be used if a number of transmit time intervals assigned inthe first uplink grant is greater than a predefined threshold. In oneembodiment, the predefined threshold is greater than or equal to anuplink scheduling delay.

In another embodiment, the gap is a time domain gap, a position of thegap is a predefined position relative to an end of the first radioresources assigned for the first multi-TTI uplink transmission by thefirst uplink grant, and the method of operation of the radio networknode further includes determining that the gap is not to be used if theposition of the gap is prior to a start of the first radio resourcesassigned by the first uplink grant.

In another embodiment, the method of operation of the radio network nodefurther includes determining that the gap is to be used if an uplinktraffic level of a corresponding cell served by the radio network nodeis greater than a predefined threshold.

In another embodiment, the method of operation of the radio network nodefurther includes determining that the gap is to be used if an uplinktraffic level of a corresponding cell served by the radio network nodeis greater than a first predefined threshold and a downlink trafficlevel of the corresponding cell served by the radio network node is lessthan a second predefined threshold.

In another embodiment, the method of operation of the radio network nodefurther includes determining that the gap is not to be used if a fixeddownlink subframe that can be used to provide the second uplink grantoccurs within the first radio resources assigned for the first multi-TTIuplink transmission.

In one embodiment, multiple subframes spanned by the first radioresources assigned for the first multi-TTI uplink transmission are thesame subframes as those spanned by radio resources assigned formulti-TTI uplink transmissions by multiple wireless devices, and the gapis the same gap as that configured for the multiple wireless devices.

In one embodiment, a method of operation of a wireless device operatingaccording to a TDD scheme in a cellular communications network isprovided. In one embodiment, the method of operation of the wirelessdevice includes receiving a first uplink grant from a radio network nodethat assigns first radio resources for a first multi-TTI uplinktransmission and listening for a second uplink grant from the radionetwork node during a gap in the first radio resources assigned for thefirst multi-TTI uplink transmission. In one embodiment, listening for asecond uplink grant comprises receiving a second uplink grant from theradio network node during the gap in the first radio resources assignedfor the first multi-TTI uplink transmission. In one embodiment, thesecond uplink grant assigns second radio resources for a secondmulti-TTI uplink transmission. In one embodiment, by utilizing the gap,uplink radio resources assigned for uplink transmission to the radionetwork node can be maximized, which is particularly beneficial in highuplink traffic conditions.

In one embodiment, the first radio resources assigned by the firstuplink grant comprise a first set of consecutive subframes, and the gapin the first radio resources comprises a gap subframe within the firstset of consecutive subframes.

In one embodiment, the method of operation of the wireless devicefurther includes performing a first portion of the first multi-TTIuplink transmission prior to listening for a second uplink grant duringthe gap and performing a remaining portion of the first multi-TTI uplinktransmission after listening for a second uplink grant during the gap.

In one embodiment, the gap is a time domain gap, and a position of thegap is a position relative to an end of the first radio resourcesassigned for the first multi-TTI uplink transmission by the first uplinkgrant. In one embodiment, an amount of time between the gap and the endof the first radio resources is greater than or equal to an uplinkscheduling delay. In another embodiment, the gap is a time domain gap,and a position of the gap is defined by a cellular communicationsnetwork standard. In another embodiment, the method of operation of thewireless device further includes receiving signaling including anindication of a position of the gap from the radio network node. In oneembodiment, the signaling is RRC signaling.

In one embodiment, a position of the gap is semi-statically configured.In another embodiment, a position of the gap is semi-staticallyconfigured individually for the wireless device. In another embodiment,a position of the gap is semi-statically configured for a plurality ofwireless devices including the wireless device.

In one embodiment, the method of operation of the wireless devicefurther includes receiving a dynamic configuration of the gap. In oneembodiment, receiving the dynamic configuration of the gap includesreceiving a position of the gap in the first uplink grant. In anotherembodiment, receiving the dynamic configuration of the gap includesreceiving an indication of the gap in the first uplink grant.

In one embodiment, the method of operation of the wireless devicefurther includes, prior to listening for a second uplink grant duringthe gap, determining whether the gap is to be used. The method ofoperation of the wireless device further includes listening for a seconduplink grant during the gap in response to determining that the gap isto be used. In one embodiment, the method of operation of the wirelessdevice further includes determining that the gap is to be used if anumber of Transmit Time Intervals (TTIs) assigned in the first uplinkgrant are greater than a predefined threshold. In one embodiment, thepredefined threshold is greater than or equal to an uplink schedulingdelay.

In another embodiment, the gap is a time domain gap, a position of thegap is a predefined position relative to an end of the first radioresources assigned for the first multi-TTI uplink transmission by thefirst uplink grant, and the method of operation of the wireless devicefurther includes determining that the gap is not to be used if theposition of the gap is prior to a start of the first radio resourcesassigned by the first uplink grant.

In another embodiment, the method of operation of the wireless devicefurther includes determining that the gap is not to be used if a fixeddownlink subframe that can be used to receive the second uplink grantoccurs within the first radio resources assigned for the first multi-TTIuplink transmission.

In one embodiment, a radio network node operating according to a TDDscheme in a cellular communications network is provided. In oneembodiment, the radio network node includes a transceiver, a processorassociated with the transceiver, and a memory containing instructionsexecutable by the processor whereby the radio network node is operativeto transmit, via the transceiver, a first uplink grant that assignsfirst radio resources for a first multi-TTI uplink transmission, andtransmit, via the transceiver, a second uplink grant that assigns secondradio resources for a second multi-TTI uplink transmission during a gapin the first radio resources assigned for the first multi-TTI uplinktransmission. The instructions may be such that the radio network nodemay be further operative to perform any of the methods of operation of aradio network node discussed above.

In another embodiment, the radio network node is adapted to transmit afirst uplink grant that assigns first radio resources for a firstmulti-TTI uplink transmission, and transmit a second uplink grant thatassigns second radio resources for a second multi-TTI uplinktransmission during a gap in the first radio resources assigned for thefirst multi-TTI uplink transmission. The radio network node may befurther adapted to perform any of the methods of operation of a radionetwork node discussed above.

In another embodiment, the radio network node includes a means fortransmitting a first uplink grant that assigns first radio resources fora first multi-TTI uplink transmission, and a means for transmitting asecond uplink grant that assigns second radio resources for a secondmulti-TTI uplink transmission during a gap in the first radio resourcesassigned for the first multi-TTI uplink transmission.

In another embodiment, a computer program is provided that includesinstructions which, when executed on at least one processor of a radionetwork node, cause the at least one processor of the radio network nodeto carry out any of the methods of operation of a radio network nodediscussed above. In another embodiment, a carrier containing theaforementioned computer program is provided, where the carrier is one ofan electronic signal, an optical signal, a radio signal, or a computerreadable storage medium (e.g., a non-transitory computer readablemedium).

In one embodiment, a wireless device operating according to a TDD schemein a cellular communications network is provided. In one embodiment, thewireless device includes a transceiver, a processor associated with thetransceiver, and a memory containing instructions executable by theprocessor whereby the wireless device is operative to receive, via thetransceiver, a first uplink grant from a radio network node that assignsfirst radio resources for a first multi-TTI uplink transmission, andlisten, via the transceiver, for a second uplink grant from the radionetwork node during a gap in the first radio resources assigned for thefirst multi-TTI uplink transmission. In one embodiment, the wirelessdevice receives a second uplink grant from the radio network node thatassigns second radio resources for a second multi-TTI uplinktransmission during the gap in the first radio resources assigned forthe first multi-TTI uplink transmission. The instructions may be suchthat the wireless device may be further operative to perform any of themethods of operation of a wireless device discussed above.

In another embodiment, the wireless device is adapted to receive a firstuplink grant from a radio network node that assigns first radioresources for a first multi-TTI uplink transmission, and listen for asecond uplink grant from the radio network node that assigns secondradio resources for a second multi-TTI uplink transmission during a gapin the first radio resources assigned for the first multi-TTI uplinktransmission. In one embodiment, the wireless device receives a seconduplink grant from the radio network node that assigns second radioresources for a second multi-TTI uplink transmission during the gap inthe first radio resources assigned for the first multi-TTI uplinktransmission. The wireless device may be further adapted to perform anyof the methods of operation of a wireless device discussed above.

In another embodiment, the wireless device includes a means forreceiving a first uplink grant from a radio network node that assignsfirst radio resources for a first multi-TTI uplink transmission, and ameans for listening for a second uplink grant from the radio networknode that assigns second radio resources for a second multi-TTI uplinktransmission during the gap in the first radio resources assigned forthe first multi-TTI uplink transmission. In one embodiment, the meansfor listening for a second uplink grant includes a means for receiving asecond uplink grant from the radio network node that assigns secondradio resources for a second multi-TTI uplink transmission during thegap in the first radio resources assigned for the first multi-TTI uplinktransmission.

In another embodiment, a computer program is provided that includesinstructions which, when executed on at least one processor of awireless device, cause the at least one processor of the wireless deviceto carry out any of the methods of operation of a wireless devicediscussed above. In another embodiment, a carrier containing theaforementioned computer program is provided, where the carrier is one ofan electronic signal, an optical signal, a radio signal, or a computerreadable storage medium (e.g., a non-transitory computer readablemedium).

Those skilled in the art will appreciate the scope of the presentdisclosure and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 illustrates a number of uplink and downlink allocations definedin Release 11 of the 3rd Generation Partnership Project (3GPP) Long TermEvolution (LTE) specifications;

FIG. 2 illustrates a radio frame structure for Time Division Duplexing(TDD) operation in 3GPP LTE, where the radio frame structure includes aspecial subframe inserted between downlink and uplink subframes;

FIG. 3 illustrates an uplink scheduling delay between a subframe duringwhich a wireless device receives an uplink grant and a time at which acorresponding uplink assignment begins;

FIG. 4 illustrates a multiple Transmit Time Interval (multi-TTI) uplinkgrant;

FIG. 5 illustrates a problem with conventional multi-TTI uplink grantswhere the uplink scheduling delay results in the number of subframesallocated for uplink transmission not being maximized;

FIG. 6 illustrates a cellular communications network in which an uplinkand a downlink between a base station and a wireless device are providedaccording to a TDD scheme and in which a gap is created in an uplinkassignment of a multi-TTI uplink grant in order to enable transmissionand reception of a next uplink grant according to one embodiment of thepresent disclosure;

FIG. 7 illustrates one example of a gap subframe according to oneembodiment of the present disclosure;

FIGS. 8A and 8B illustrate the operation of the base station and thewireless device of FIG. 6 according to one embodiment of the presentdisclosure;

FIG. 9 illustrates a process by which the wireless device of FIG. 6creates a gap subframe at a position defined by a corresponding cellularcommunications network standard according to one embodiment of thepresent disclosure;

FIG. 10 illustrates a process by which the wireless device of FIG. 6creates a gap subframe at a position configured by the cellularcommunications network according to one embodiment of the presentdisclosure;

FIGS. 11A and 11B illustrate the operation of the base station and thewireless device of FIG. 6 according to one embodiment in which a gapsubframe is configured dynamically in a multi-TTI uplink grant;

FIG. 12 illustrates one example in which a gap subframe is configured ina multi-TTI uplink grant according to the process of FIG. 11;

FIGS. 13A and 13B illustrate the operation of the base station toselectively use gap subframes according to one embodiment of the presentdisclosure;

FIG. 14 illustrates a process by which the base station determineswhether to use gaps based on an uplink traffic level according to oneembodiment of the present disclosure;

FIG. 15 illustrates one example in which a gap is not used for the nextuplink grant when the uplink traffic level is not high according to oneembodiment of the present disclosure;

FIGS. 16A through 16C illustrate the operation of the base station toselectively use gap subframes according to another embodiment of thepresent disclosure;

FIG. 17 illustrates one example of a new multi-TTI uplink granttransmitted in a fixed downlink subframe;

FIG. 18A through 18C illustrate the operation of the wireless device ofFIG. 6 according to one embodiment of the present disclosure;

FIG. 19 illustrates the operation of the base station to schedulemultiple wireless devices with the same length of consecutive uplinksubframes and the same gap configuration according to one embodiment ofthe present disclosure;

FIG. 20 is a functional block diagram of the base station and thewireless device of FIG. 6 according to one embodiment of the presentdisclosure;

FIG. 21 is a block diagram of the base station of FIG. 6 according toone embodiment of the present disclosure; and

FIG. 22 is a block diagram of the wireless device of FIG. 6 according toone embodiment of the present disclosure.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the embodiments andillustrate the best mode of practicing the embodiments. Upon reading thefollowing description in light of the accompanying drawing figures,those skilled in the art will understand the concepts of the disclosureand will recognize applications of these concepts not particularlyaddressed herein. It should be understood that these concepts andapplications fall within the scope of the disclosure and theaccompanying claims.

Time Division Duplexing (TDD) schemes in current cellular communicationsnetworks such as, for example, 3rd Generation Partnership Project (3GPP)Long Term Evolution (LTE) Release 11 (Rel-11) networks, suffer from anumber of problems. More specifically, LTE Rel-11 uses a number ofpredefined fixed allocations of uplink and downlink subframes, where amaximum of 60% of the total subframes can be used for uplink datatransmission. In a TDD cell with only or heavy uplink traffic at aparticular point in time, the predefined fixed downlink subframes, whichare a minimum of 40% of the total subframes, cannot be used for uplinktraffic. As such, spectrum efficiency in the TDD cell is not optimizedas it does not match the uplink/downlink traffic balance. On the otherhand, even with heavy uplink traffic, some downlink subframes are stillneeded in order to transmit uplink grants for uplink data transmissionsas well as to provide a reverse link for higher layer protocolsdepending on a service being provided.

To maximize the radio resources used for uplink traffic in a TDD cellwith only or heavy uplink traffic, the number of downlink subframesneeds to be reduced. Multiple Transmit Time Interval (multi-TTI) uplinkscheduling can be used to further reduce the need for downlink subframesthat contain uplink grants. In the current LTE specifications, themaximum number of uplink subframes that can be scheduled by a multi-TTIuplink grant is two subframes. Two subframes are not enough. As such,multi-TTI uplink grants that schedule more than two uplink subframesand, in particular, many subframes are desired.

When using multi-TTI uplink grants that schedule many uplink subframesto handle high uplink traffic, a problem occurs at the end of thescheduled period of uplink subframes due to the uplink scheduling delay(g). In particular, if many consecutive uplink subframes are scheduledby a multi-TTI uplink grant in a dynamic TDD system, then a new, ornext, uplink grant must be transmitted in a downlink subframe after thescheduled period of uplink subframes. Then, due to the uplink schedulingdelay (g), several subframes after the downlink subframe containing thenew uplink grant cannot be used for uplink data transmission. As aresult, system resources allocated for the uplink traffic are notmaximized. An example that illustrates this problem is provided in FIG.5. As illustrated in FIG. 5, a first period of uplink subframes(subframes 5-16) is scheduled by a first multi-TTI uplink grant (notshown). Subframe 17 is then used as a downlink subframe to transmit asecond multi-TTI uplink grant. However, due to the uplink schedulingdelay (g), which in this example is 4 subframes, uplink transmissioncannot be scheduled to begin until subframe 22. As a result, subframes18-21 are not used for uplink transmission and, as such, systemresources allocated for the uplink traffic are not maximized.

Systems and methods are disclosed herein that can be used to maximizeresources allocated for uplink traffic when using multi-TTI uplinkgrants, particularly in scenarios with only uplink traffic or heavyuplink traffic. In this regard, FIG. 6 illustrates a cellularcommunications network 10 including a base station 12 and one or morewireless devices 14. The base station 12 is a high power base station(e.g., an Evolved Node B (eNB) serving a macro cell) or a low power basestation (e.g., a micro, pico, or home/femto eNB). The base station 12serves a corresponding cell (e.g., a macro cell, a micro cell, a picocell, or a femto cell) of the cellular communications network 10. Notethat while the embodiments described herein are described with respectto the base station 12, the embodiments may be used for other types ofradio network nodes (e.g., remote radio heads, access points (e.g., aWi-Fi system where the roles of base station and wireless device are notstatic), etc.). Also, while the base station 12 and the wirelessdevice(s) 14 are discussed herein, the concepts disclosed herein arealso applicable to Device-to-Device (D2D) communications between twowireless devices 14. The wireless device(s) 14 can be any type ofdevice(s) equipped with a wireless interference for transmitting anuplink to and receiving a downlink from the base station 12. Note thatwhile only one base station 12 is illustrated for clarity and ease ofdiscussion, the cellular communications network 10 typically includesmany base stations 12. In one embodiment, the cellular communicationsnetwork 10 is a 3GPP LTE network and, as such, 3GPP LTE terminology issometimes used herein. However, the embodiments disclosed herein can beused in any type of wireless network that utilizes TDD (dynamic ornon-dynamic) and multi-TTI uplink scheduling.

The base station 12 and the wireless device(s) 14 communicate accordingto a TDD scheme. In one embodiment, the TDD scheme is a dynamic TDDscheme. However, the embodiments disclosed herein are also applicable tonon-dynamic TDD. As discussed in detail below, according to the dynamicTDD scheme, multiple (m) future subframes are scheduled in the uplinkfrom the wireless device 14 by a multi-TTI uplink grant transmitted bythe base station 12 in a single downlink subframe. There is a non-zerouplink scheduling delay of g subframes after an uplink grant (e.g., amulti-TTI uplink grant) is transmitted in a downlink subframe by thebase station 12 until the wireless device 14 can begin to transmituplink data. A value for the uplink scheduling delay (g) is selected toprovide sufficient time for decoding of the uplink grant in the wirelessdevice 14 and preparation of the next uplink transmission in thewireless device 14.

The dynamic TDD for the downlink and uplink between the base station 12and the wireless device 14 may be configured (e.g., by higher layersignaling such as Radio Resource Control (RRC) signaling from the basestation 12 to the wireless device 14) or specified by a correspondingstandard to have a few fixed downlink subframes that can never be usedfor uplink transmission. Positions of the fixed downlink subframes maybe configured or defined by the corresponding standard. The positions ofthe fixed downlink subframes may be defined, e.g., relative tosynchronization signals such as, for instance, the PrimarySynchronization Signal (PSS) or the Secondary Synchronization Signal(SSS) in LTE. Naturally, subframes where the base station 12 transmitssynchronization signals (e.g., PSS and SSS) are fixed downlinksubframes. However, there may also be other fixed downlink subframesthat do not contain synchronization signals. For example, fixed downlinksubframes may also be used for broadcast control messages from the basestation 12 used for connection establishment between the base station 12and the wireless device 14. The remaining subframes (i.e., the subframesother than the fixed downlink subframes) can be dynamically allocatedfor either downlink or uplink, depending on scheduling commands (i.e.,downlink assignments and uplink grants) from the base station 12 to thewireless device 14. As such, the base station 12 can quickly adapt theuplink and downlink relative to traffic loads.

Note that, in some scenarios, the base station 12 transmits a multi-TTIuplink grant to the wireless device 14 that schedules uplinktransmission for the wireless device 14 in multiple (m) consecutivesubframes where a fixed downlink subframe occurs inside this set of msubframes. When this happens, the wireless device 14 cannot transmitduring the fixed downlink subframe, but can continue afterwards ifscheduled to do so. In this case, there are two alternatives tointerpret the multi-TTI uplink grant of the multiple (m) consecutivesubframes, namely: (a) the wireless device 14 continues to transmit theremaining subframes according to its uplink grant after the fixeddownlink subframe for a total of m uplink subframes or (b) the wirelessdevice 14 considers one uplink subframe punctured by the fixed downlinksubframe such that the transmission effectively contains one lesssubframe scheduled in the uplink grant (i.e., m−1 subframes are actuallytransmitted by the wireless device 14 in the uplink).

In order to ensure continuous uplink scheduling without interruptiondespite the non-zero scheduling delay (g), a gap subframe is introducedin the set of m consecutive scheduled uplink subframes. In the gapsubframe, the wireless device 14 does not transmit. Instead, thewireless device 14 monitors the downlink control channel from the basestation 12 for a new uplink grant. The wireless device 14 may alsoreceive a downlink shared data channel in the gap subframe if scheduledby the base station 12. Due to the gap subframe, the wireless device 14can detect a new uplink grant with sufficient time before a transmissionperiod of the new uplink grant begins (i.e., the gap subframe is atleast g subframes prior to an end of the period of subframes assigned bythe previous multi-TTI uplink grant).

FIG. 7 illustrates one example of a gap subframe according to oneembodiment of the present disclosure. In this example, the base station12 previously transmitted a multi-TTI uplink grant (not shown) toschedule multiple (m) consecutive subframes for uplink transmission fromthe wireless device 14. In the particular example, m is equal to 13, andthe subframes scheduled by the previous multi-TTI uplink grant aresubframes 5-17. Subframes 5-17 are referred to herein as an uplinkassignment of, or made by, the previous multi-TTI uplink grant or aperiod of subframes scheduled by the previous multi-TTI uplink grant.

A gap subframe (G) is introduced into the multiple (m) consecutivesubframes scheduled by the previous multi-TTI uplink grant. In thisembodiment, a position of the gap is relative to an end of the uplinkassignment of the previous multi-TTI uplink grant. In particular, theposition of the gap is a number (d) of subframes from the end of theuplink assignment, where in this example d∈{g, . . . , m}. In otherwords, for best efficiency and no interruption in uplink transmission bythe wireless device 14, the position of the gap subframe (G) is greaterthan or equal to g subframes from the end of the uplink assignment andless than or equal to m subframes from the end of the uplink assignment(i.e., g≤d≤m). In one example, the position of the gap subframe (G)relative to the end of the uplink assignment is equal to the uplinkscheduling delay (g) (i.e., d=g≤m). Note however, that the position ofthe gap subframe (G) (as defined by, in this example, d) can be anyposition prior to the last subframe in the uplink assignment (i.e.,1<d<m). However, positions where 1<d<g will result in subframes betweenthe two uplink assignments that cannot be used for uplink transmission,but the number of such subframes will be reduced as compared to thatusing conventional uplink scheduling techniques (i.e., an uplink grantin the subframe following the end of the previous uplink assignment).

A new multi-TTI uplink grant for a wireless device 14 is transmitted inthe downlink from the base station 12 in the gap subframe (G) to providea new uplink assignment for that wireless device 14. Note that the newmulti-TTI uplink grant may be for the same wireless device 14 as theprevious uplink grant or a different wireless device 14. By positioningthe gap subframe (G) at g≤d≤m or, in one example, d=g≤m, the new uplinkgrant can start the new uplink assignment for the corresponding wirelessdevice 14 in the subframe immediately following the end of the previousuplink assignment (i.e., the new uplink assignment can begin at subframe18 as illustrated in this example). As a result, subframes that cannotbe used for uplink transmission between the previous and new uplinkassignments can be avoided, which in turn maximizes the amount ofsubframes for uplink transmission.

The position of the gap subframe (G) can be defined in any suitablemanner. In one embodiment, the position of the gap subframe (G) withinthe uplink assignment is defined by a corresponding cellularcommunications network standard (e.g., a 3GPP LTE standard). In anotherembodiment, the position of the gap subframe (G) within the uplinkassignment is signaled by the cellular communications network 10 (e.g.,signaled via RRC signaling from the base station 12 to the wirelessdevice 14 or included in the multi-TTI uplink assignment). Additionally,in some embodiments, one or more rules may be defined such that theposition and/or presence of the gap subframe (G) depend on one or morecriteria. For example, a rule may be defined that states that the gapsubframe (G) is not present if the number (m) of subframes in thecorresponding uplink assignment is less than a threshold (or converselyis present if the number (m) of subframes in the corresponding uplinkassignment is greater than or equal to a threshold). This threshold maybe, for example, the uplink scheduling delay (g) or the relativeposition (d) of the gap subframe (G) (if present) from the end of thecorresponding uplink assignment. As another example, a rule may bedefined that states that the gap subframe (G) is not present if a fixeddownlink subframe that can be used to transmit a new uplink grant fallswithin the corresponding uplink assignment and, in some embodiments, hasa position that satisfies one or more defined criteria (e.g., positionrelative to the end of the corresponding uplink assignment is greaterthan or equal to the uplink scheduling delay (g)).

FIGS. 8A and 8B illustrates the operation of the base station 12 and thewireless device 14 according to one embodiment of the presentdisclosure. In FIG. 8A, the first uplink grant and the new uplink grantduring the gap are for the same wireless device 14. As illustrated inFIG. 8A, the base station 12 transmits a first multi-TTI uplink grant tothe wireless device 14 in a downlink subframe (step 100A). Notably, amulti-TTI uplink grant is also referred to herein as an uplink grant fora multi-TTI uplink transmission. The multi-TTI uplink grant assignsmultiple (m) consecutive uplink subframes for a first uplinktransmission by the wireless device 14. In response, the wireless device14 performs the first uplink transmission according to the firstmulti-TTI uplink grant (step 102A). During the first uplinktransmission, the wireless device 14 creates a gap subframe withinmultiple (m) consecutive uplink subframes assigned for the first uplinktransmission during which the wireless device 14 listens for a downlinkincluding a new uplink grant for the wireless device 14 (step 104A). Asdiscussed above, the position of the gap subframe may be predefined(e.g., by a standard) or signaled to the wireless device 14 (e.g., viaRRC signaling).

During the gap subframe, the base station 12 transmits and the wirelessdevice 14 receives a new, or second, multi-TTI uplink assignment for thewireless device 14 (step 106A). The wireless device 14 then continuesthe first uplink transmission according to the first multi-TTI uplinkgrant (step 108A). Notably, in one embodiment, the wireless device 14transmits a total of m uplink subframes, not including the gap subframe.In another embodiment, the wireless device transmits in m−1 uplinksubframes (i.e., the downlink subframe is counted toward the mconsecutive subframes assigned by the first multi-TTI uplink grant). Inthe same manner, any fixed downlink subframe(s) that occur within theuplink assignment may or may not be counted toward the m subframesscheduled for the first uplink transmission.

After completing the first uplink transmission on the multiple (m)consecutive uplink subframes assigned by the first multi-TTI uplinkgrant, the wireless device 14 performs a second uplink transmissionaccording to the second multi-TTI uplink grant (step 110A). As discussedabove, in one embodiment, the position of the gap subframe within themultiple (m) consecutive subframes assigned by the first multi-TTIuplink grant is such that an amount of time or subframes between the gapsubframe and the end of the multiple (m) consecutive subframes assignedby the first multi-TTI uplink grant is greater than or equal to theuplink scheduling delay (g). As a result, the second uplink transmissioncan be scheduled to begin in the subframe immediately following the endof the first uplink transmission. In this manner, usage of radioresources for uplink transmission is maximized.

In the embodiment of FIG. 8B, the first uplink grant and the new uplinkgrant during the gap are for different wireless devices 14. Asillustrated in FIG. 8B, the base station 12 transmits a first multi-TTIuplink grant to a first wireless device 14 in a downlink subframe (step100B). Notably, a multi-TTI uplink grant is also referred to herein asan uplink grant for a multi-TTI uplink transmission. The multi-TTIuplink grant assigns multiple (m) consecutive uplink subframes for afirst uplink transmission by the first wireless device 14. In response,the first wireless device 14 performs the first uplink transmissionaccording to the first multi-TTI uplink grant (step 102B). During thefirst uplink transmission, the first wireless device 14 creates a gapsubframe within multiple (m) consecutive uplink subframes assigned forthe first uplink transmission during which the first wireless device 14listens for a downlink including a new uplink grant for the wirelessdevice 14 (step 104B). As discussed above, the position of the gapsubframe may be predefined (e.g., by a standard) or signaled to thewireless device 14 (e.g., via RRC signaling).

During the gap subframe, the base station 12 transmits a new, or second,multi-TTI uplink grant for a second wireless device 14, and the secondwireless device 14 receives the second multi-TTI uplink grant (step106B). After the gap subframe, the first wireless device 14 thencontinues the first uplink transmission according to the first multi-TTIuplink grant (step 108B). Notably, in one embodiment, the first wirelessdevice 14 transmits a total of m uplink subframes, not including the gapsubframe. In another embodiment, the first wireless device 14 transmitsin m−1 uplink subframes (i.e., the downlink subframe is counted towardthe m consecutive subframes assigned by the first multi-TTI uplinkgrant). In the same manner, any fixed downlink subframe(s) that occurwithin the uplink assignment may or may not be counted toward the msubframes scheduled for the first uplink transmission.

In response to the second uplink grant, the second wireless device 14performs an uplink transmission according to the second multi-TTI uplinkgrant (step 110B). As discussed above, in one embodiment, the positionof the gap subframe within the multiple (m) consecutive subframesassigned by the first multi-TTI uplink grant is such that an amount oftime or subframes between the gap subframe and the end of the multiple(m) consecutive subframes assigned by the first multi-TTI uplink grantis greater than or equal to the uplink scheduling delay (g). As aresult, the second uplink transmission can be scheduled to begin in thesubframe immediately following the end of the first uplink transmission.In this manner, usage of radio resources for uplink transmission ismaximized.

As discussed above, the position of the gap subframe can be defined ordetermined in any suitable manner. FIG. 9 illustrates a process by whichthe wireless device 14 creates the gap subframe at a position defined bya corresponding cellular communications network standard according toone embodiment of the present disclosure. As illustrated, the wirelessdevice 14 determines the position of the gap subframe as defined by thestandard (step 200). In one example, the standard defines the positionof the gap subframe relative to the end of the corresponding uplinkassignment, e.g., d subframes from an end of the multiple (m)consecutive subframes assigned by the multi-TTI uplink grant asdiscussed above. Further, the position and/or presence of the gapsubframe may be further defined by the standard based on one or morerules, as discussed above. The wireless device 14 then creates the gapsubframe within the uplink transmission for the multi-TTI uplink grant(step 202). The wireless device 14 creates the gap subframe by utilizingthe gap subframe as a downlink subframe during which the wireless device14 listens for a new uplink grant.

FIG. 10 illustrates a process by which the wireless device 14 createsthe gap subframe at a position configured by the cellular communicationsnetwork 10 according to one embodiment of the present disclosure. Asillustrated, in this embodiment, the base station 12 signals a gapconfiguration to the wireless device 14 via, e.g., RRC signaling (step300). The gap configuration may be broadcast to multiple wirelessdevices 14 or transmitted individually to the wireless device 14. Inthis manner, the gap subframe can be, e.g., semi-statically configured.The gap configuration includes an indication that the gap subframe is tobe used and/or the position of the gap subframe within uplinkassignments for multi-TTI uplink grants. The wireless device 14 thencreates the gap subframe during the uplink transmission for a multi-TTIuplink grant, as discussed above (step 302). Note that, while notillustrated, the gap configuration is signaled to the wireless device 14before the multi-TTI uplink grant is transmitted to the wireless device14. Further, in one embodiment, the gap configuration applies tomultiple (e.g., all) multi-TTI uplink grants (e.g., all multi-TTI uplinkgrants or all multi-TTI uplink grants that satisfy one or more rules,e.g., m>d).

FIGS. 11A and 11B illustrate the operation of the base station 12 andthe wireless device 14 where the gap subframe is configured dynamicallyin the multi-TTI uplink grant according to another embodiment of thepresent disclosure. In FIG. 11A, the first uplink grant and the seconduplink grant are for the same wireless device 14. More specifically, asillustrated, the base station 12 transmits a first multi-TTI uplinkgrant to the wireless device 14 in a downlink subframe, where the firstmulti-TTI uplink grant includes a gap configuration (step 400A). Themulti-TTI uplink grant assigns multiple (m) consecutive uplink subframesfor a first uplink transmission by the wireless device 14. The gapconfiguration configures a presence of a gap subframe within themultiple (m) consecutive subframes scheduled by the first multi-TTIuplink grant (i.e., whether a gap subframe is to be created/present ornot) and/or a position of the gap subframe within the multiple (m)consecutive uplink subframes assigned by the first multi-TTI uplinkgrant. In one embodiment, the gap configuration is included in adownlink gap subframe control message included in the first multi-TTIuplink grant.

The wireless device 14 then performs the first uplink transmissionaccording to the first multi-TTI uplink grant (step 402A). During thefirst uplink transmission, the wireless device 14 creates a gapsubframe, as configured by the gap configuration, within the multiple(m) consecutive uplink subframes assigned for the first uplinktransmission during which the wireless device 14 listens for a downlinkincluding a new uplink grant for the wireless device 14 (step 404A). Inone embodiment, the position of the gap subframe is indicated in the gapconfiguration. In another embodiment, the gap configuration indicatesthat the gap subframe is to be used, but the position of the gapsubframe is otherwise defined (e.g., defined by a standard or RRCsignaling). Further, the use of the gap subframe may be conditioned onone or more additional rules. For example, the gap configuration may beignored by the wireless device 14 (i.e., the gap subframe is notcreated) if, e.g., the position of the gap subframe is prior to abeginning, or start, of the multiple (m) consecutive uplink subframesscheduled by the multi-TTI uplink grant (e.g., if d>m).

During the gap subframe, the base station 12 transmits and the wirelessdevice 14 receives a new, or second, multi-TTI uplink assignment for thewireless device 14 (step 406A). The second multi-TTI uplink grant mayinclude a gap configuration for a corresponding uplink assignment. Thewireless device 14 then continues the first uplink transmissionaccording to the first multi-TTI uplink grant (step 408A). Again, notethat in one embodiment the wireless device 14 transmits a total of muplink subframes in the first uplink transmission, not including the gapsubframe. In another embodiment, the wireless device 14 transmits in m−1uplink subframes in the first uplink transmission (i.e., the gapsubframe is counted toward the m subframes assigned by the firstmulti-TTI uplink grant). In the same manner, any fixed downlinksubframe(s) that occur within the uplink assignment may or may not becounted toward the m subframes scheduled for the first uplinktransmission.

After completing the first uplink transmission on the multiple (m)consecutive uplink subframes assigned by the first multi-TTI uplinkgrant, the wireless device 14 performs a second uplink transmissionaccording to the second multi-TTI uplink grant (step 410A). As discussedabove, in one embodiment, the position of the gap subframe within themultiple (m) consecutive subframes assigned by the first multi-TTIuplink grant is such that an amount of time or subframes between the gapsubframe and the end of the multiple (m) consecutive subframes assignedby the first multi-TTI uplink grant is greater than or equal to theuplink scheduling delay (g). As a result, the second uplink transmissioncan be scheduled to begin in the subframe immediately following the endof the first uplink transmission. In this manner, usage of radioresources for uplink transmission is maximized.

In FIG. 11B, the first uplink grant and the second uplink grant are fordifferent wireless devices 14. More specifically, as illustrated, thebase station 12 transmits a first multi-TTI uplink grant to a firstwireless device 14 in a downlink subframe, where the first multi-TTIuplink grant includes a gap configuration (step 400B). The multi-TTIuplink grant assigns multiple (m) consecutive uplink subframes for afirst uplink transmission by the first wireless device 14. The gapconfiguration configures a presence of a gap subframe within themultiple (m) consecutive subframes scheduled by the first multi-TTIuplink grant (i.e., whether a gap subframe is to be created/present ornot) and/or a position of the gap subframe within the multiple (m)consecutive uplink subframes assigned by the first multi-TTI uplinkgrant. In one embodiment, the gap configuration is included in adownlink gap subframe control message included in the first multi-TTIuplink grant.

The first wireless device 14 then performs the first uplink transmissionaccording to the first multi-TTI uplink grant (step 402B). During thefirst uplink transmission, the first wireless device 14 creates a gapsubframe, as configured by the gap configuration, within the multiple(m) consecutive uplink subframes assigned for the first uplinktransmission during which the first wireless device 14 listens for adownlink including a new uplink grant for the first wireless device 14(step 404B). In one embodiment, the position of the gap subframe isindicated in the gap configuration. In another embodiment, the gapconfiguration indicates that the gap subframe is to be used, but theposition of the gap subframe is otherwise defined (e.g., defined by astandard or RRC signaling). Further, the use of the gap subframe may beconditioned on one or more additional rules. For example, the gapconfiguration may be ignored by the first wireless device 14 (i.e., thegap subframe is not created) if, e.g., the position of the gap subframeis prior to a beginning, or start, of the multiple (m) consecutiveuplink subframes scheduled by the multi-TTI uplink grant (e.g., if d>m).

During the gap subframe, the base station 12 transmits a new, or second,multi-TTI uplink grant for a second wireless device 14, and the secondwireless device 14 receives the second multi-TTI uplink grant (step406B). The second multi-TTI uplink grant may include a gap configurationfor a corresponding uplink assignment. After the gap, the first wirelessdevice 14 then continues the first uplink transmission according to thefirst multi-TTI uplink grant (step 408B). Again, note that in oneembodiment the first wireless device 14 transmits a total of m uplinksubframes in the first uplink transmission, not including the gapsubframe. In another embodiment, the first wireless device 14 transmitsin m−1 uplink subframes in the first uplink transmission (i.e., the gapsubframe is counted toward the m subframes assigned by the firstmulti-TTI uplink grant). In the same manner, any fixed downlinksubframe(s) that occur within the uplink assignment may or may not becounted toward the m subframes scheduled for the first uplinktransmission.

In response to receiving the second uplink grant, the second wirelessdevice 14 performs a second uplink transmission according to the secondmulti-TTI uplink grant (step 410B). As discussed above, in oneembodiment, the position of the gap subframe within the multiple (m)consecutive subframes assigned by the first multi-TTI uplink grant issuch that an amount of time or subframes between the gap subframe andthe end of the multiple (m) consecutive subframes assigned by the firstmulti-TTI uplink grant is greater than or equal to the uplink schedulingdelay (g). As a result, the second uplink transmission can be scheduledto begin in the subframe immediately following the end of the firstuplink transmission. In this manner, usage of radio resources for uplinktransmission is maximized.

FIG. 12 illustrates one example in which a gap subframe is configured ina multi-TTI uplink grant according to the process of FIG. 11. Asillustrated, a first multi-TTI uplink grant (uplink grant A) istransmitted to the wireless device 14 in the downlink during subframe A.Uplink grant A includes a gap indicator (“Gap”) that is set to a valueof “1” to thereby indicate that a gap subframe is to be created duringthe multiple (m) consecutive uplink subframes scheduled by uplink grantA. In this example, uplink grant A schedules subframes 5-17 as uplinksubframes (i.e., m=13). Further, the position of the gap subframe, inthis example, is defined as d=g, where g=5. The position of the gapsubframe may also be indicated in uplink grant A or may be otherwisedefined (e.g., by a standard or RRC signaling). In response to uplinkgrant A, the wireless device 14 performs uplink transmission insubframes 5-12, creates a gap subframe at subframe 13 for reception of anew uplink grant (uplink grant B), and continues uplink transmission insubframes 14-17. Notably, in this example, the gap subframe countstoward the multiple (m) consecutive uplink subframes scheduled by uplinkgrant A and, as such, the wireless device 14 performs uplinktransmission in m−1 subframes. Uplink grant B schedules the next uplinktransmission (for the same wireless device 14 or a different wirelessdevice 14) starting at, in this example, subframe 18. As such, subframesbetween the two uplink transmissions that cannot be used for the uplinkare avoided, which in turn maximizes the resources used for the uplink.

FIGS. 13A and 13B illustrate the operation of the base station 12 toselectively use gap subframes according to one embodiment of the presentdisclosure. A gap subframe will add more TDD switching at the basestation 12 and the wireless device 14. Each TDD switching needs a guardperiod to switch from uplink to downlink and vice versa. System capacitycan be reduced if there are many TDD switching events in a short periodof time. As such, in one embodiment, gap subframes are only used whenuplink traffic in the cell served by the base station 12 is heavy (andin some embodiments downlink traffic is light) and many consecutiveuplink subframes are needed for uplink traffic.

More specifically, as illustrated, the base station 12 determineswhether to use gap subframes (step 500). As discussed below, in oneexample, the base station 12 determines that gap subframes are to beused if uplink traffic is heavy and, in some embodiments, if downlinktraffic is light. However, additional or alternative criteria may beused. If gap subframes are to be used, the base station 12 operates asdescribed above. In particular, the base station 12 sends, or transmits,a multi-TTI uplink grant (step 502). The base station 12 then transmitsa new uplink grant (e.g., a new multi-TTI uplink grant) for the samewireless device 14 or a different wireless device 14 in a gap subframecreated in the multiple (m) consecutive uplink subframes scheduled bythe multi-TTI uplink grant of step 502 (step 504). As discussed above,in one embodiment, the position of the gap subframe is defined by astandard. In another embodiment, the position of the gap subframe isdetermined by the network (e.g., by the base station 12) and signaled tothe wireless device 14 by higher layer signaling (e.g., RRC signaling)or within the multi-TTI uplink grant of step 502.

In this example, the base station 12 then determines whether it is timeto re-evaluate the decision to use gap subframes (step 506). Forinstance, the base station 12 may periodically re-evaluate the decisionto use gap subframes (e.g., every N seconds). If it is not time tore-evaluate, the base station 12 returns to step 504 and sends the nextuplink grant (e.g., the next multi-TTI uplink grant). Once it is time tore-evaluate, the process returns to step 500. Note that step 506 is justan example. For instance, in one alternative embodiment, the basestation 12 determines whether a gap subframe is to be used prior totransmission of each multi-TTI uplink grant. This may be particularlybeneficial if the gap configuration is included in the uplink grant.

Returning to step 500, if the base station 12 determines that gapsubframes are not to be used, the base station 12 sends, or transmits, amulti-TTI uplink grant (or a single TTI uplink grant) (step 508). Notethat if gap subframes are dynamically configured in the multi-TTI uplinkgrants, the multi-TTI uplink grant of step 508 may include an indicationthat that gap subframe is not to be used in the corresponding uplinkassignment. In this example, the base station 12 then determines whetherit is time to re-evaluate the decision to not use gap subframes (step510). For instance, the base station 12 may periodically re-evaluate thedecision as to whether to use gap subframes (e.g., every N seconds). Ifit is not time to re-evaluate, the base station 12 returns to step 508and sends the next uplink grant. Once it is time to re-evaluate, theprocess returns to step 500. Note that step 510 is just an example. Forinstance, in one alternative embodiment, the base station 12 determineswhether a gap subframe is to be used prior to transmission of eachuplink grant. This may be particularly beneficial if the gapconfiguration is included in the uplink grant.

FIG. 14 illustrates step 500 of FIG. 13A in more detail according to oneembodiment of the present disclosure. In order to determine whether gapsubframes are to be used, the base station 12 determines whether uplinktraffic in the cell served by the base station 12 is greater than apredefined uplink threshold that is indicative of heavy uplink traffic(step 600). If so, the base station 12 determines whether downlinktraffic in the cell served by the base station 12 is less than apredefined threshold that is indicative of low downlink traffic (step602). If so, the base station 12 determines that gap subframes are to beused (step 604). Otherwise, if the uplink traffic is not greater thanthe uplink threshold or the downlink traffic is not less than thedownlink threshold, then the base station 12 determines that gaps arenot to be used (step 606). Note that, for the decisions in steps 600 and602, the uplink traffic level and the downlink traffic level can bedetermined in any suitable manner. Techniques for doing so will be knownto one of ordinary skill in the art upon reading this disclosure.However, in one embodiment, the uplink and downlink traffic levels areexpressed as corresponding percentages of system resources utilized forthe uplink and downlink, respectively, during a defined period of time.

FIG. 15 illustrates one example in which the uplink traffic is not heavyand, as a result, a gap subframe is not used. In this example, subframes5-10 are downlink subframes. As a result of a previous multi-TTI uplinkgrant, the wireless device 14 transmits in the uplink during subframes11-16. However, since uplink traffic is not heavy, no gap subframe isused. As such, a new uplink grant is not transmitted until after the endof the multiple (m) subframes scheduled by the previous multi-TTI uplinkgrant. In this particular example, the new uplink grant is transmittedin subframe 17, which is the subframe immediately following the end ofthe multiple (m) subframes scheduled by the previous uplink grant. Thenew uplink grant schedules the next uplink transmission starting atsubframe 22.

In the embodiments described above, gap subframes are used fortransmission (by the base station 12) and reception (by the wirelessdevice 14) of a new uplink grant for the same or a different wirelessdevice 14. However, in another embodiment, the new uplink grant may betransmitted in a fixed downlink subframe that occurs within the multiple(m) uplink subframes scheduled by the previous uplink grant. In thiscase, the base station 12 may determine that a gap subframe is not to beused in the corresponding uplink assignment. Conversely, the wirelessdevice 14 may ignore, or not use, the gap subframe and, instead, use thegap subframe as an uplink subframe (or as a downlink subframe in whichthe wireless device 14 does not necessarily listen for a new uplinkgrant). However, in one embodiment, if the gap subframe is configured,the wireless device 14 listens for a new uplink grant (and possibly adownlink grant) in both the gap subframe and the fixed downlinksubframe.

In this regard, FIGS. 16A through 16C illustrate the operation of thebase station 12 to determine whether to use gap subframes based on thepresence of a suitable fixed downlink subframe for transmission of a newuplink grant according to one embodiment of the present disclosure. Asillustrated, the base station 12 determines whether to use a gapsubframe (step 700). In this embodiment, the base station 12 determinesthat a gap subframe is to be used if there is no fixed downlink subframein multiple (m) uplink subframes to be scheduled by an upcomingmulti-TTI uplink grant. The fixed downlink subframe may be required tomeet one or more conditions for being suitable for a new uplink grantsuch as, for example, d≥g. In addition, the base station 12 may considerone or more rules for determining whether to use a gap subframe (e.g.,heavy uplink traffic condition).

If a gap subframe is to be used, the base station 12 operates asdescribed above. In particular, the base station 12 sends, or transmits,a multi-TTI grant to a wireless device 14 to schedule the multiple (m)consecutive uplink subframes (step 702). In this embodiment, themulti-TTI uplink grant of step 702 preferably includes a gapconfiguration to indicate whether a gap subframe is to be used in adynamic manner. The base station 12 then transmits a new uplink grant(e.g., a new multi-TTI uplink grant) for the same wireless device 14 ora different wireless device 14 in a gap subframe created in the multiple(m) consecutive uplink subframes scheduled by the multi-TTI uplink grantof step 702 (step 704). As discussed above, in one embodiment, theposition of the gap subframe is defined by a standard. In anotherembodiment, the position of the gap subframe is determined by thenetwork (e.g., by the base station 12) and signaled to the wirelessdevice 14 by higher layer signaling (e.g., RRC signaling) or within themulti-TTI uplink grant of step 702. In this example, the base station 12then returns to step 700.

Returning to step 700, if the base station 12 determines that a gapsubframe is not to be used, the base station 12 determines whether afixed downlink subframe is configured for the wireless device 14 withinthe multiple (m) consecutive subframes to be scheduled for the wirelessdevice 14 (step 706). As discussed above, the fixed downlink subframemay be required to also satisfy one or more criteria for being suitablefor a new uplink grant (e.g., d≥g). If there is a suitable fixeddownlink subframe, the base station 12 sends, or transmits, a multi-TTIgrant to the wireless device 14 to schedule the multiple (m) consecutiveuplink subframes (step 708). The base station 12 then transmits a newuplink grant (e.g., a new multi-TTI uplink grant) for the same ordifferent wireless device 14 in the fixed downlink subframe within themultiple (m) consecutive uplink subframes scheduled by the multi-TTIuplink grant of step 708 (step 710). The process then returns to step700. Returning to step 706, if there is no suitable fixed downlinksubframe, the base station 12 sends, or transmits, a multi-TTI uplinkgrant (or single TTI uplink grant) to the wireless device 14 (step 712).Any new uplink grant will thereafter be sent in a downlink subframe thatoccurs after (e.g., immediately after) the multiple (m) consecutiveuplink subframes assigned by the multi-TTI uplink grant of step 712.After step 712, the process then returns to step 700.

FIG. 17 illustrates one example of a new multi-TTI uplink granttransmitted in a fixed downlink subframe. In this example, a firstmulti-TTI uplink grant (uplink grant A) schedules a first uplinktransmission for the wireless device 14 on subframes 5-17. In thisexample, subframe 13 is a fixed downlink subframe (D). As such, uplinkgrant A includes a gap configuration of Gap=0 to thereby indicate to thewireless device 14 that a gap subframe is not to be created. Rather, aseither signaled by the network or otherwise defined (e.g., via astandard), a new multi-TTI uplink grant (uplink grant B) is to betransmitted by the base station 12 in the fixed downlink subframe, whichagain in this example is subframe 13. As such, during the first uplinktransmission, the wireless device 14 stops uplink transmission andmonitors the downlink in subframe 13 to thereby listen for uplink grantB. In this example, uplink grant B is a multi-TTI uplink grant forsubframes 18-25. Note, however, that if the gap subframe is configured(i.e., in this example, Gap=1), then the wireless device 14 listens fora new uplink grant in both the gap subframe and the fixed downlinksubframe.

Thus, in the embodiments of FIGS. 16A through 16C and FIG. 17, if afixed downlink subframe is configured, the base station 12 can transmita new uplink multi-TTI grant in the fixed downlink subframe.Alternatively, the base station 12 may transmit the new uplink multi-TTIgrant in a gap subframe even if there is a fixed downlink subframe(e.g., when the fixed downlink subframe is not at an optimal or desiredposition in the uplink assignment). If the new multi-TTI uplink grant istransmitted in fixed downlink subframe, the gap subframe is optional.The use of the gap subframe, even when a fixed downlink subframe isused, can be controlled by a gap configuration (e.g., a downlink gapsubframe control message) in the uplink grant. Note that a fixeddownlink subframe can also be used as gap subframe if the positions ofthe gap subframe and the fixed subframe coincide.

FIGS. 18A through 18C illustrate the operation of the wireless device 14according to one embodiment of the present disclosure. This embodimentis similar to that of FIGS. 16A through 16C, but from the perspective ofthe wireless device 14. As illustrated, the wireless device 14 receivesa multi-TTI uplink grant (step 800). The wireless device 14 determineswhether a gap subframe is to be created in the multiple (m) consecutiveuplink subframes scheduled by the multi-TTI uplink grant of step 800(step 802). In one embodiment, the multi-TTI uplink grant of step 800includes a gap configuration that indicates to the wireless device 14whether a gap subframe is to be used and, in some embodiments, theposition of the gap subframe. Further, even if the use of a gap subframeis configured, the wireless device 14 may further apply one or morecriteria or rules to determine whether to ignore the gap subframe ornot. For instance, the wireless device 14 may decide to ignore, or notcreate, the gap subframe if the position of the gap subframe is prior tothe uplink assignment (e.g., if d>m).

If a gap subframe is to be created, the wireless device 14 operates asdescribed above. In particular, the wireless device 14 performs uplinktransmission on those uplink subframes scheduled by the multi-TTI uplinkgrant of step 800 prior to the position of the gap subframe (step 804).The wireless device 14 then creates the gap subframe at the desiredposition (step 806). During the gap subframe, the wireless device 14listens for a new multi-TTI uplink grant from the base station 12 (step808). The wireless device 14 may or may not receive a new multi-TTIuplink grant during the gap subframe. The wireless device 14 thencontinues uplink transmission on the remaining subframes of themulti-TTI uplink grant of step 800 (step 810). Once uplink transmissionis complete, the process returns to step 802 and is repeated for thenext uplink transmission.

Returning to step 802, if a gap subframe is not to be created, thewireless device 14 determines whether there is a fixed downlink subframewithin the multiple (m) consecutive uplink subframes scheduled by themulti-TTI uplink grant of step 800 (step 812). The fixed downlinksubframe may be required to meet one or more predefined criteria (e.g.,d≥g). If there is a fixed downlink subframe, the wireless device 14performs uplink transmission on those uplink subframes scheduled by themulti-TTI uplink grant of step 800 prior to the position of the fixeddownlink subframe (step 814). The wireless device 14 then switches todownlink reception for the fixed downlink subframe, and listens for anew multi-TTI uplink grant from the base station 12 during the fixeddownlink subframe (step 816). The wireless device 14 may or may notreceive a new multi-TTI uplink grant during the fixed downlink subframe.The wireless device 14 then continues uplink transmission on theremaining subframes of the multi-TTI uplink grant of step 800 (step818). Once uplink transmission is complete, the process returns to step802 and is repeated for the next uplink transmission. Returning to step812, if there is no fixed downlink subframe, the wireless device 14performs uplink transmission on the multiple (m) uplink subframesscheduled by the multi-TTI uplink grant of step 800 (step 820). Theprocess then returns to step 800 to receive the next uplink grant.

FIG. 19 illustrates the operation of the base station 12 to schedulemultiple wireless devices 14 with the same length of m consecutiveuplink subframes and the same gap configuration according to oneembodiment of the present disclosure. As illustrated, the base station12 (and in particular a scheduler of the base station 12) sends, ortransmits, multi-TTI uplink grants to multiple wireless devices 14(steps 900-1 through 900-M). The multi-TTI uplink grants are such thatthe wireless devices 14 are scheduled for the same length (m) ofconsecutive subframes and the same gap configuration. As a result, allof the wireless devices 14 have an aligned subframe direction in thesame cell. This may be particularly beneficial in a TDD system. If thewireless devices 14 have uplink data buffers of different sizes (i.e.,they desire to transmit different amounts of uplink data), the schedulerof the base station 12 may, in one embodiment, ensure that scheduledbandwidths for the wireless devices 14 are adapted so that the amount ofcoded data to be transmitted is mapped to m subframes.

FIG. 20 is a functional block diagram of the base station 12 and thewireless device 14 according to one embodiment of the presentdisclosure. As illustrated, the base station 12 includes an uplinkscheduling module 16 that may be implemented in hardware, software(e.g., software stored in a computer readable medium such as anon-transistor computer readable medium (e.g., memory) and executed byone or more processors of the base station 12), or a combinationthereof. The uplink scheduling module 16 operates to provide thefunctionality of the base station 12 according to any one of theembodiments described herein. Further, the uplink scheduling module 16may include one or more sub-modules such as, e.g., a first module fortransmitting a first uplink grant and a second module for transmitting asecond uplink grant during a gap subframe created in the multiple (m)consecutive subframes assigned by the first uplink grant.

The wireless device 14 includes an uplink grant reception module 18, agap creation module 20, and an uplink transmission module 22 thattogether operate to provide the functionality of the wireless device 14according to any of the embodiments described herein. The uplink grantreception module 18, the gap creation module 20, and the uplinktransmission module 22 may be implemented in hardware, software (e.g.,software stored in a computer readable medium such as a non-transistorcomputer readable medium (e.g., memory) and executed by one or moreprocessors of the wireless device 14), or a combination thereof. As anexample, in one embodiment, the uplink grant reception module 18operates to receive a first multi-TTI uplink grant (e.g., via a receiverof the wireless device 14). The uplink transmission module 22 thenperforms uplink transmission (e.g., via a transmitter of the wirelessdevice 14) using the radio resources assigned by the first multi-TTIuplink grant. During uplink transmission, the gap creation module 20creates a gap subframe during which the uplink grant reception module 18receives a new uplink grant. The uplink transmission module 22 thencompletes the uplink transmission for the first multi-TTI uplink grant.

FIG. 21 is a block diagram of the base station 12 according to oneembodiment of the present disclosure. As illustrated, the base station12 includes a radio controller 24 including a processor 26, memory 28,and a network interface 30 and radio equipment 32 including atransceiver 34 coupled to one or more antennas 36. In one embodiment,the functionality of the base station 12, according to any one of theembodiments described above, is implemented in software stored on anon-transitory computer readable medium (e.g., the memory 28) andexecuted by the processor 26. In one particular embodiment, the uplinkscheduling module 16 of FIG. 20 is implemented in software stored in thememory 28 and executed by the processor 26.

In another embodiment, a computer program is provided that includesinstructions which, when executed on at least one processor of the basestation 12 (e.g., the processor 26), cause the at least one processor ofthe base station 12 to carry out any of the embodiments describedherein. In another embodiment, a carrier containing the aforementionedcomputer program is provided, where the carrier is one of an electronicsignal, an optical signal, a radio signal, or a computer readablestorage medium (e.g., a non-transitory computer readable medium).

FIG. 22 is a block diagram of the wireless device 14 according to oneembodiment of the present disclosure. As illustrated, the wirelessdevice 14 includes a processor 38, memory 40, and a transceiver 42coupled to one or more antennas 44. In one embodiment, the functionalityof the wireless device 14, according to any one of the embodimentsdescribed above, is implemented in software stored on a non-transitorycomputer readable medium (e.g., the memory 40) and executed by theprocessor 38. In one particular embodiment, the uplink grant receptionmodule 18, the gap creation module 20, and the uplink transmissionmodule 22 of FIG. 20 are implemented in software stored in the memory 40and executed by the processor 38.

In another embodiment, a computer program is provided that includesinstructions which, when executed on at least one processor of thewireless device 14 (e.g., the processor 38), cause the at least oneprocessor of the wireless device 14 to carry out any of the embodimentsdescribed herein. In another embodiment, a carrier containing theaforementioned computer program is provided, where the carrier is one ofan electronic signal, an optical signal, a radio signal, or a computerreadable storage medium (e.g., a non-transitory computer readablemedium).

While not being limited to any particular advantage(s), certainimplementations of at least some of the embodiments described hereinprovide the following advantages. These advantages are only examples andare not intended to be an exhaustive list of all advantages of theembodiments described herein. In one embodiment, a control messageincluded in the uplink grant provides a very small extra controlsignaling overhead and can dynamically allocate a gap subframe for newuplink multi-TTI grant between consecutive scheduled uplink subframes.The subframes used for uplink traffic can be maximized with shortscheduling delay. Further, in some embodiments, when the traffic in thesystem is not uplink heavy, the gap subframe is not configured so theamount of TDD switching in the system is reduced.

The following acronyms are used throughout this disclosure.

3GPP 3^(rd) Generation Partnership Project

D2D Device-to-Device

DFT Discrete Fourier Transform

eNB Evolved Node B

EPDCCH Enhanced Physical Downlink Control Channel

E-UTRA Evolved Universal Terrestrial Radio Access

GP Guard Period

LTE Long Term Evolution

LTE Rel-11 Long Term Evolution Release 11

ms Millisecond

multi-TTI Multiple Transmit Time Interval

OFDM Orthogonal Frequency Division Multiplexing

PDCCH Physical Downlink Control Channel

PDSCH Physical Downlink Shared Channel

PSS Primary Synchronization Signal

PUSCH Physical Uplink Shared Channel

RRC Radio Resource Control

SC-FDMA Single Carrier Frequency Division Multiple Access

SSS Secondary Synchronization Signal

TDD Time Division Duplex

TS Technical Specification

TTI Transmission Time Interval

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present disclosure. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

What is claimed is:
 1. A radio network node operating according to aTime Division Duplexing, TDD, scheme in a cellular communicationsnetwork, the radio network node comprising: a transceiver; a processorassociated with the transceiver; and memory containing instructionsexecutable by the processor, whereby the radio network node is operativeto: while operating according to the TDD scheme: transmit, to a wirelessdevice via the transceiver, a first uplink grant that assigns firstradio resources for a first multiple transmit time interval uplinktransmission; and transmit, to the wireless device via the transceiver,a second uplink grant during a gap in the first radio resources assignedfor the first multiple transmit time interval uplink transmission,wherein the first radio resources comprise a set of consecutivesubframes, wherein the gap is a time domain gap within the set ofconsecutive subframes during which an uplink transmission on the firstradio resources is interrupted, and wherein the gap comprises acontiguous gap spanning at least one of the subframes within the set ofconsecutive subframes.
 2. The radio network node of claim 1 wherein aposition of the gap is a position relative to an end of the first radioresources assigned for the first multiple transmit time interval uplinktransmission by the first uplink grant.
 3. The radio network node ofclaim 2 wherein an amount of time between the gap and the end of thefirst radio resources is greater than or equal to an uplink schedulingdelay.
 4. The radio network node of claim 1 wherein a position of thegap is defined by a cellular communications network standard.
 5. Theradio network node of claim 1 further comprising signaling a position ofthe gap to one or more wireless devices.
 6. The radio network node ofclaim 1 wherein a position of the gap is semi-statically configured forindividual wireless devices and/or for a plurality of wireless devices.7. The radio network node of claim 1 further comprising dynamicallyconfiguring the gap.
 8. The radio network node of claim 1 furtheroperative to, prior to transmitting the second uplink grant during thegap, determining whether the gap is to be used, wherein transmitting thesecond uplink grant comprises transmitting the second uplink grantduring the gap in response to determining that the gap is to be used. 9.The radio network node of claim 1 wherein a plurality of subframesspanned by the first radio resources assigned for the first multipletransmit time interval uplink transmission are the same subframes asthose spanned by radio resources assigned for multiple transmit timeinterval uplink transmissions by a plurality of wireless devices, andthe gap is the same gap as that is configured for the plurality ofwireless devices.
 10. A wireless device operating according to a TimeDivision Duplexing, TDD, scheme in a cellular communications network,the wireless device comprising: a transceiver; a processor associatedwith the transceiver; and memory containing instructions executable bythe processor, whereby the wireless device is operative to: whileoperating according to the TDD scheme: receive, via the transceiver, afirst uplink grant from a radio network node that assigns first radioresources for a first multiple transmit time interval uplinktransmission; and interrupting an uplink transmission on the first radioresources to listen, via the transceiver, for a second uplink grant fromthe radio network node during a gap in the first radio resourcesassigned for the first multiple transmit time interval uplinktransmission, wherein the first radio resources comprise a set ofconsecutive subframes, wherein the gap is a time domain gap within theset of consecutive subframes, and wherein the gap comprises a contiguousgap spanning at least one of the subframes within the set of consecutivesubframes.
 11. The wireless device of claim 10 further comprising:performing a first portion of the first multiple transmit time intervaluplink transmission prior to the gap; and performing a remaining portionof the first multiple transmit time interval uplink transmission afterthe gap.
 12. The wireless device of claim 10 wherein a position of thegap is a position relative to an end of the first radio resourcesassigned for the first multiple transmit time interval uplinktransmission by the first uplink grant.
 13. The wireless device of claim12 wherein an amount of time between the gap and the end of the firstradio resources is greater than or equal to an uplink scheduling delay.14. The wireless device of claim 10 wherein a position of the gap isdefined by a cellular communications network standard.
 15. The wirelessdevice of claim 10 further comprising receiving signaling comprising anindication of a position of the gap from the radio network node.
 16. Thewireless device of claim 10 wherein a position of the gap issemi-statically configured for individual wireless devices and/or for aplurality of wireless devices.
 17. The wireless device of claim 10further comprising receiving a dynamic configuration of the gap.
 18. Thewireless device of claim 10 further operative to, prior to listening forthe second uplink grant during the gap, determining whether the gap isto be used, wherein listening for the second uplink grant compriseslistening for the second uplink grant during the gap in response todetermining that the gap is to be used.